Hematite has been used as a colorant for centuries. It is the most common type of naturally occurring iron oxide mineral. Examples of hematites include hematites, pyrites, and magnetites, which are respectively red-colored, yellow-colored, and black-colored. Hematites are mostly prepared as synthetic products, and thus are used in various fields as pigments having clear color tones and excellent durability, being inexpensive and having low toxicity and high stability. In particular, well-known synthetic hematite pigments include red or red brown-colored hematite particle powder (α-Fe2O3 or micaceous iron oxide (MIO)), yellow or deep brown-colored maghemite (γ-Fe2O3) particle powder, and black-colored magnetite (FeOx-Fe2O3 where 0<×<=1). Many of the processes proposed so far for preparing such products comprise at least one drawbacks such as being not cost effective, not being environmental friendly or being complicated.
There is thus a need for at least providing an alternative to the existing solutions for preparing hematites. Moreover, there would be a need for valorizing certain waste materials and at least partially convert them into hematite.